Most people do that because of performance problems, bugs and
annoying effects (wobbly, genie)
Nobody turns off composition on MacOSX because it works seamlessly.
We should strive to reach that degree of robustness and performance
on Linux too, as we're already 5 years late.

- Do we care about the huge increase in power consumption ?

Hmmm... I never thought it would be an issue once we remove
various source inefficiency.
A composited desktop shouldn't necessarily cause much more GPU
or CPU activity than traditional graphics plus the needed
hand-made double buffering hacks to hide flickering during
repaints.
--
// Bernardo Innocenti
\X/ http://www.codewiz.org/